Air motors are known to have a number of working chambers to which compressed gas is delivered to drive pistons at least partly enclosing the working chambers. Valve mechanisms co-ordinate the delivery of compressed air sequentially to the chambers as well as provide for exhausting air from the chambers to cause reciprocation of the pistons. Typically the pistons are connected by a single shaft, with the pistons reciprocating along the axis of the shaft.
A disadvantage of known air motors is the valve assemblies. The valve assemblies consist of a large number of components. This increases the cost in respect of production, and storage of spare parts, and undesirably increase the size of the air motor.
A further disadvantage of known air motors is that the exhaust port and inlet port are part of the main valve assembly. Should either of these ports become damaged during connection or disconnection with associated hosing, then it is necessary to replace the entire valve assembly.